On Wednesday, November 8, 2017 at 7:45:11 PM UTC-5, Phil Allison wrote:
David Farber wrote:

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** Good servicing practice requires that you FIRST observe a fault
before delving inside to find the cause.

Consider that the unit may have no fault at all, the reported noises
being fed in from an external device and / or are due to AC supply
transients.


.... Phil


I would agree with you up until the point where after several days of
waiting, and no faults are exhibited, then a peek inside the unit might give
you a clue. Maybe something spilled inside, or perhaps another tech might
have done some creative repairs.


** The flaw with that idea is that you will very often find something odd looking and wrongly assume it must be the cause of the reported fault - when it is not.

False alarm reports are VERY common with guitar amps and accessories plus also with disco equipment and PA gear.

If after a reasonable time running and testing a unit, it shows no sign of the reported fault then it becomes the owner's problem to DEMONSTRATE the fault to the repairer.





.... Phil

The difference is: An amp in service is loaded, unloaded, lifted, carried, vibrated, kicked, and otherwise physically abused.

An amp in the shop sits quietly on a bench or on a shelf with nothing to disturb it.

A customer who puts equipment into the hands of a tech - and is thereby spending money has no reason to create a false (and possibly costly) alarm. An Honest Tech is obligated to take the customer at their word. Hence the advice to check for visible defects, to tap the parts with a diddle-stick or similar - in other words, go looking for trouble. Further, and Honest Tech who has been around a while will kinda-sorta have a good idea where to start based on historical experience. And an Honest Tech, when confronted with obvious 'not right' things will correct them - within the minimum charge limit at the very least.

Peter Wieck
Melrose Park, PA